Water vapor barrier coating agent and laminate

Abstract

To provide: a water vapor barrier coating agent that is highly safe and has excellent water vapor barrier properties; and a laminate.SOLUTION: The water vapor barrier coating agent contains an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium. The ratio of the amino acids in the total solid content included in the water vapor barrier coating agent is from 0.5 mass% to 40.0 mass% inclusive.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a water vapor barrier coating agent and a laminate.

Background Art

[0002] Packaging materials with paper as the base material and imparted with water vapor barrier properties and gas barrier properties (particularly, oxygen barrier properties) have been conventionally used to prevent deterioration of the quality of the contents in the packaging of foods, medical products, electronic components, etc.

[0003] As a method of imparting water vapor barrier properties and gas barrier properties to a paper base material, a method of laminating a synthetic resin film or a metal foil excellent in gas barrier properties with the paper as a support is common. However, materials obtained by laminating a synthetic resin film or the like on a paper base material have problems in terms of the environment, such as the difficulty of recycling paper, synthetic resin, etc. after use, and the microplastic problem. Therefore, development of water vapor barrier materials and gas barrier materials based on paper without using a synthetic resin film or the like has been underway. For example, Patent Document 1 discloses a paper barrier material in which a water vapor barrier layer and a gas barrier layer are provided in this order on a paper base material. The water vapor barrier layer contains a layered inorganic compound, a cationic resin, and an anionic binder resin.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, packaging materials for foods have been required to use a water vapor barrier coating agent using safer additives instead of a more safe cationic resin. However, the cationic resin forming the water vapor barrier layer described in Patent Document 1 is a non-edible material.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a water vapor barrier coating agent and a laminate having high safety and excellent water vapor barrier properties.

Means for Solving the Problems

[0007] That is, the present invention has the following configuration. [1] A water vapor barrier coating agent containing an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium, wherein the proportion of the amino acids in the total solid content contained in the water vapor barrier coating agent is 0.5% by mass or more and 40.0% by mass or less. [2] The water vapor barrier coating agent according to [1], wherein the polymer serving as the backbone of the anionic binder resin is preferably an olefin-unsaturated carboxylic acid copolymer. [3] A laminate obtained by coating a paper substrate with the water vapor barrier coating agent according to [1] or [2].

Effects of the Invention

[0008] The water vapor barrier coating agent and the laminate of the present invention have high safety and excellent water vapor barrier properties. Amino acids are units that constitute proteins in living organisms, and many of the essential and non-essential amino acids that constitute human proteins are approved as food additives and can be said to be highly safe materials.

Modes for Carrying Out the Invention

[0009] <Water Vapor Barrier Coating Agent> The water vapor barrier coating agent of the present invention contains an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium.

[0010] <Anionic Binder Resin> The anionic binder resin has a function of dispersibility of the inorganic layered compound, and a binder resin modified with a monomer containing an acid group such as a carboxylic acid is preferable. Examples of the polymer serving as the backbone of the binder resin include styrene-butadiene copolymers, styrene-acrylic copolymers, methacrylate-butadiene copolymers, acrylonitrile-butadiene copolymers, olefin-unsaturated carboxylic acid copolymers, acrylic ester polymers, and the like. Among these, at least one selected from the group consisting of styrene-butadiene copolymers, styrene-acrylic copolymers, and olefin-unsaturated carboxylic acid copolymers is preferable because of good water resistance, good elongation, and difficulty in generating cracks in the coating layer due to folding. More preferably, it is an olefin-unsaturated carboxylic acid copolymer. From the viewpoint of handling, the form of the anionic binder resin is preferably an aqueous dispersion.

[0011] The styrene-butadiene copolymer is a copolymer obtained by emulsion polymerization of monomers composed of aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, chlorostyrene, and the like, conjugated diene compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and other compounds copolymerizable therewith. Styrene is preferable as the aromatic vinyl compound, and 1,3-butadiene is preferable as the conjugated diene compound. As the styrene-butadiene copolymer, Nipol SX1105A (trade name, manufactured by Zeon Corporation, Japan) and the like are commercially available and can be easily obtained and used.

[0012] Styrene-acrylic copolymers are copolymers obtained by emulsion polymerization of monomers consisting of aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, chlorostyrene, etc., unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid, etc., unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as monoethyl itaconate, monobutyl fumarate and monobutyl maleate, unsaturated sulfonic acid monomers or their salts such as acrylamidopropanesulfonic acid, sodium acrylate sulfethyl salt, sodium methacrylate sulfopropyl salt, etc., and other compounds copolymerizable therewith. As the aromatic vinyl compound, styrene etc. are suitable, and as the unsaturated carboxylic acid monomer, unsaturated sulfonic acid monomer or their salt, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, etc. are suitable. Styrene-acrylic copolymers are commercially available as Joncryl PDX 7741 (trade name, manufactured by BASF Japan) etc., and can be easily obtained and used.

[0013] The olefin-unsaturated carboxylic acid copolymer is a copolymer obtained by emulsion polymerization of monomers composed of olefins, especially α-olefins such as ethylene and propylene, and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid, unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as monoethyl itaconate, monobutyl fumarate, and monobutyl maleate, unsaturated sulfonic acid monomers or their salts such as acrylamidopropanesulfonic acid, sodium acrylate sulfonatoethyl salt, and sodium methacrylate sulfopropyl salt, and other compounds copolymerizable therewith. As the olefin, α-olefins, especially ethylene and the like are preferred. As the unsaturated carboxylic acid monomer, unsaturated sulfonic acid monomer or its salt, acrylic acid, methacrylic acid, itaconic acid, fumaric acid and the like are preferred. Specific examples of the olefin-unsaturated carboxylic acid copolymer include, for example, an aqueous dispersion of an ethylene-acrylic acid copolymer ammonium salt, which is commercially available as Zeicen AC, Zeicen A, etc. (trade names, manufactured by Sumitomo Seika Chemical Co., Ltd.) and can be easily obtained and used.

[0014] The content ratio of the anionic binder resin is not particularly limited. Among the total solid content contained in the water vapor barrier coating agent, 20% by mass or more is preferable, 40% by mass or more is more preferable, 50% by mass or more is further preferable, and 60% by mass or more is particularly preferable. On the other hand, the content ratio of the anionic binder resin is preferably 95% by mass or less, more preferably 85% by mass or less, among the total solid content contained in the water vapor barrier coating agent.

[0015] <Amino acids> Many amino acids are approved as food additives, have high safety, and have a dispersing effect on inorganic layered compounds, so they can improve the water vapor barrier property. Examples of amino acids include amino acids and amino acid derivatives such as valine, leucine, isoleucine, phenylalanine, tryptophan, lysine, histidine, methionine, threonine, glycine, alanine, proline, aspartic acid, glutamic acid, asparagine, glutamine, tyrosine, arginine, cysteine, serine, etc. Also, dipeptides such as carnosine, anserine, homanserine, kyotorphin, valenin, aspartame, glolin, valetine, pseudoproline, etc., tripeptides such as isenin, glutathione, isoleucine-proline-proline, leupeptin, melanostatin, ophthamic acid, norophthamic acid, etc., and oligopeptides such as amanitin, antipain, ceruletide, glutathione, netropsin, pepstatin, peptide T, phalloidin, teprotide, tuftsin, etc. may be used. Further, homopolymers of amino acids such as polyvaline, polyleucine, polyisoleucine, polyphenylalanine, polytryptophan, polylysine, polyhistidine, polyglycine, polyalanine, polyproline, polyaspartic acid, polyglutamic acid, polytyrosine, polyarginine, etc. may be used. Or a copolymer combining the above amino acids may be used. Amino acids may be used alone or in combination of a plurality.

[0016] The content ratio of amino acids is 0.5% by mass or more and 40.0% by mass or less in the total solid content contained in the water vapor barrier coating agent. The content ratio of amino acids is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less in the total solid content contained in the water vapor barrier coating agent.

[0017] <Inorganic layered compound> The inorganic layered compound may be either a natural product or a synthetic product, or a mixture thereof. Examples of natural products include smectite-based clay minerals such as montmorillonite, kaolinite (kaolin mineral), pyrophyllite, talc, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite, and mica-based clay minerals such as bentonite, pure mica, and brittle mica. Examples of synthetic products include synthetic hectorite (sodium magnesium silicate), synthetic bentonite, synthetic saponite, and synthetic mica. Among these, from the viewpoint of improving dispersibility, at least one selected from the group consisting of water-swellable montmorillonite, bentonite, synthetic mica, synthetic hectorite, and synthetic bentonite is preferable. From the viewpoint of improving barrier properties, montmorillonite, synthetic mica, and synthetic hectorite are more preferable. The inorganic layered compound may be used alone or in combination of a plurality thereof.

[0018] The content ratio of the inorganic layered compound is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, and particularly preferably 20% by mass or less in the total solid content contained in the water vapor barrier coating agent. On the other hand, the content ratio of the inorganic layered compound is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 5% by mass or more in the total solid content contained in the water vapor barrier coating agent.

[0019] <aqueous medium> The aqueous medium may be only water, or an aqueous medium in which water is mixed with water-miscible organic solvents such as alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol and their alkyl ether derivatives, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0020] <other additives> Dispersants, surfactants, defoamers, wetting agents, dyes, color modifiers, thickeners, etc. can be added to the water vapor barrier coating agent as needed.

[0021] <Method for producing water vapor barrier coating agent> As a method for producing a water vapor barrier coating agent using the above constituent materials, there is no particular limitation. For example, (1) an inorganic layered compound (which may be previously swollen and exfoliated in a dispersion medium such as water), amino acids, and an aqueous medium are added to an anionic binder resin solution and mixed, and the inorganic layered compound is dispersed using a stirrer or a dispersing device; (2) after swelling and exfoliating the inorganic layered compound in a dispersion medium such as water, an anionic binder resin solution, amino acids, and an aqueous medium are added to the dispersion (dispersion solution) in which the inorganic layered compound has been exfoliated and dispersed using a stirrer or a dispersing device; (3) after swelling and exfoliating the inorganic layered compound in a dispersion medium such as water, amino acids are added, and an anionic binder resin solution and an aqueous medium are added to the dispersion (dispersion solution) in which the inorganic layered compound has been exfoliated and dispersed using a stirrer or a dispersing device. These methods can be mentioned.

[0022] The above stirrers and dispersing devices are not particularly limited as long as they are ordinary stirrers and dispersing devices, and the inorganic layered compound can be uniformly dispersed in the dispersion using these. However, from the viewpoint of obtaining a transparent and stable inorganic layered compound dispersion, it is preferable to use a high-pressure disperser, an ultrasonic disperser, etc. Examples of high-pressure dispersers include Nanomizer (trade name, manufactured by Nanomizer Co., Ltd.), Microfluidizer (trade name, manufactured by Microfluidics Corp.), Altimizer (trade name, manufactured by Sugino Machine Ltd.), DeBEE (trade name, manufactured by BEE Co., Ltd.), Niro Soavi Homogenizer (trade name, manufactured by Niro Soavi Co., Ltd.), etc. As the pressure conditions of these high-pressure dispersers, it is preferable to perform the dispersion treatment at 100 MPa or less. When the pressure conditions exceed 100 MPa, the inorganic layered compound is likely to be crushed, and the desired gas barrier property may decrease.

[0023] <Laminate> The laminate of the present invention has a water vapor barrier layer formed by coating and drying a water vapor barrier coating agent on at least one surface of a paper substrate. Further, when gas barrier properties are required, for example, a gas barrier layer may be provided by further coating and drying a gas barrier coating agent on the water vapor barrier layer. When providing a gas barrier layer, the water vapor barrier coating agent may be applied and the gas barrier coating agent may be applied thereon without being completely dried.

[0024] <Paper substrate> The paper substrate used for the paper substrate layer is not particularly limited as long as it is paper generally used with plant-derived pulp as the main component. Specifically, bleached or unbleached kraft paper, high-quality paper, cardboard, liner paper, coated paper, single-sided coated paper, glassine paper, graphane paper, etc. may be mentioned. The paper substrate is preferably paper mainly composed of pulp that is easily dispersed in water by mechanical dissociation action.

[0025] <Water vapor barrier layer> The water vapor barrier layer is obtained by coating and drying a water vapor barrier coating agent. The thickness of the water vapor barrier layer is preferably 1 to 30 μm, more preferably 3 to 20 μm. Further, the coating amount of the water vapor barrier layer is preferably 1 to 30 g / m 2 in terms of solid content, and more preferably 3 to 20 g / m 2 in terms of solid content.

[0026] <Gas barrier layer> The gas barrier layer is obtained by coating and drying a gas barrier coating agent. The thickness of the gas barrier layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm. Further, the coating amount of the gas barrier layer is preferably 0.1 to 10 g / m 2 in terms of solid content, and more preferably 0.5 to 7 g / m 2 in terms of solid content.

[0027] <Gas barrier coating agent> The gas barrier coating agent contains, for example, a water-soluble polymer and an aqueous medium. It may also contain an inorganic layered compound.

[0028] <Water-soluble polymer Examples of the water-soluble polymer include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinylpyrrolidone, urethane resins, polyacrylic acid and its salts, casein, polyethyleneimine, and the like. Among these, completely saponified or partially saponified polyvinyl alcohol or modified polyvinyl alcohol is preferred because of its better gas barrier properties. Examples of the modified polyvinyl alcohol include ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol. The water-soluble polymer may be used alone or in combination of two or more. The content of the water-soluble polymer is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, based on the total solid content of the gas barrier coating agent.

[0029] <Inorganic layered compound As the inorganic layered compound, the same inorganic layered compounds as those described in the water vapor barrier layer can be used for the water vapor barrier coating agent. The inorganic layered compound may be used alone or in combination of two or more. The content of the inorganic layered compound is not particularly limited, and is preferably about 1 to 40 parts by mass with respect to 100 parts by mass of the water-soluble polymer of the gas barrier coating agent. From the viewpoint of improving the barrier properties, the inorganic layered compound is preferably at least one selected from the group consisting of mica, bentonite, and kaolin.

[0030] <Aqueous medium Examples of the aqueous medium include water alone, or an aqueous medium obtained by mixing water with water-miscible organic solvents such as alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol and their alkyl ether derivatives, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0031] <Method for producing gas barrier coating agent> The method for producing a gas barrier coating agent is not particularly limited. For example, a water-soluble polymer, an inorganic layered compound, and an aqueous medium are mixed and sufficiently stirred and mixed at room temperature to prepare a gas barrier coating agent having a predetermined concentration.

[0032] <Coating method> The coating method for applying a water vapor barrier coating agent or a gas barrier coating agent is not particularly limited, and known methods can be used. Examples of the coating method include a blade coater, a bar coater, an air knife coater, a slit die coater, a gravure coater, a microgravure coater, a gate roll coater, etc. In particular, for the formation of a water vapor barrier layer, coaters that scrape the coating surface, such as a reverse gravure coater, a kiss reverse gravure coater, a blade coater, a bar coater, an air knife coater, and a slit die coater, are preferable in that they promote the orientation of the inorganic layered compound.

[0033] The drying equipment for drying the water vapor barrier coating agent or the gas barrier coating agent is not particularly limited, and known equipment can be used. Examples of the drying equipment include a hot air dryer, an infrared dryer, a gas burner, a hot plate, etc.

[0034] <Sealant layer> The laminate of the present invention has a water vapor barrier layer, or a water vapor barrier layer and a gas barrier layer on at least one surface of the paper base material layer. Further, a sealant layer may be formed on at least one outermost layer of the laminate.

[0035] The sealant layer is a layer that melts and adheres by heating or ultrasonic waves, and is a layer that can bond laminates to each other by heat sealing or the like. The sealant layer can be formed by laminating synthetic resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and polyvinyl acetate polymer by melt extrusion lamination or dry lamination methods. Also, the sealant layer can be formed by coating an emulsion dispersion of synthetic resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and polyvinyl acetate polymer. The thickness of the sealant layer is preferably 1 to 50 μm, and more preferably 3 to 30 μm. Also, the formation amount of the sealant layer is preferably 1 to 50 g / m 2 and more preferably 3 to 30 g / m 2 as the solid content.

Examples

[0036] Examples are given below to more specifically explain the water vapor barrier coating agent and laminate of the present invention, but the present invention is not limited thereto. In the examples and comparative examples, "parts" and "%" indicate "parts by mass" and "mass %", respectively, unless otherwise specified. The raw materials used in the examples and comparative examples are as follows.

[0037] <Paper substrate> OK Blizard (basis weight 70 g / m 2 , manufactured by Oji Materia Co., Ltd.) <Anionic binder resin> Ethylene-acrylic acid copolymer (trade name "Zexcen A", solid content 25 mass%, manufactured by Sumitomo Seika Chemicals Co., Ltd.) Styrene-acrylic copolymer (trade name "Joncryl PDX 7741", solid content 50 mass%, manufactured by BASF Japan Ltd.) Styrene-butadiene copolymer (trade name "Nipol SX1105A", solid content 45.5 mass%, manufactured by Zeon Corporation of Japan) <Inorganic layered compound> Synthetic mica (trade name "Somashif ME300B-4T", solid content 7.9 mass%, manufactured by Katakura Koppe Agri Co., Ltd.) Montmorillonite (trade name "Kunipia F", manufactured by Kunimine Industries Co., Ltd., dispersed in ion-exchanged water to a solid content of 4%) <Amino acids> L-Valine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Leucine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Isoleucine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Phenylalanine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Tryptophan (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Lysine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Histidine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Methionine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Threonine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Glycine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Alanine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Proline (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Aspartic acid (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Glutamic acid (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Asparagine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Glutamine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Arginine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Cysteine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Serine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Citrulline (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) Diglycine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) Triglycine (100% by mass of solid content, manufactured by Tokyo Chemical Industry Co., Ltd.) ε-Polylysine (25% by mass of solid content, manufactured by JNC Corporation)

[0038] <Method for producing water vapor barrier coating agent> An anionic binder resin, an inorganic layered compound, amino acids, and an aqueous medium were mixed in the ratios shown in Tables 1 and 2, and stirred with a stirrer to produce water vapor barrier coating agents for Examples and Comparative Examples.

[0039] <Method for producing laminate> On one surface of a paper substrate, the water vapor barrier coating agent obtained above was applied after drying so that the coating amount was 5 g / m 2 After coating with a bar coater, it was dried with a dryer air at 60 °C using a hot air dryer to form a water vapor barrier layer.

[0040] <Evaluation method> <Water vapor barrier property> The laminate obtained above was measured for water vapor transmission rate (WVTR value, g / m 2 / day) in accordance with JIS Z 0208-1976. The temperature and humidity conditions were 40 ± 0.5 °C and 90 ± 2% relative humidity. The following "◎" or "〇" was used as the acceptance criterion. [Evaluation criteria] ◎: The water vapor transmission rate decreased by 50% or more compared to the case where no amino acid was contained. 〇: The water vapor transmission rate decreased by 25% or more and less than 50% compared to the case where no amino acid was contained. △: The water vapor transmission rate decreased by more than 0% and less than 25% compared to the case where no amino acid was contained. ×: The water vapor transmission rate increased compared to the case where no amino acid was contained. Specifically, Examples 1 to 25 and Comparative Examples 5 and 6 were compared with Comparative Example 1 (636 g / m 2 / day), Example 26 was compared with Comparative Example 2 (517 g / m 2 / day), Example 27 was compared with Comparative Example 3 (120 g / m 2 / day), and Example 28 was compared with Comparative Example 4 (230 g / m 2 / day).

[0041]

Table 1

[0042]

Table 2

Claims

1. A water vapor barrier coating agent containing an anionic binder resin, an amino acid (excluding polycarboxylic acids), an inorganic layered compound, and an aqueous medium, A water vapor barrier coating agent, characterized in that a ratio of the amino acids is 0.5 mass % or more and 40.0 mass % or less based on a total solid content contained in the water vapor barrier coating agent.

2. 2. The water vapor barrier coating agent according to claim 1, wherein the polymer forming the backbone of the anionic binder resin is an olefin-unsaturated carboxylic acid copolymer.

3. A laminate comprising a paper substrate coated with the water vapor barrier coating agent according to claim 1 or 2.

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